US 3926930 A
Acrylonitrile polymer fibers having an improved hygroscopicity are prepared by hydrolyzing an acrylonitrile copolymer comprising 0.5 to 10% by weight of N,N-substituted amide, 0 - 15% by weight of an ethylenically unsaturated compound copolymerizable with acrylonitrile and at least 85% by weight of acrylonitrile in nitric acid to give a degree of hydrolysis as expressed by ODR of 1680 cm<->1 to 1450 cm<->1 in the range of 1.2 - 1.8, followed by conventional wet spinning by using nitric acid as a solvent.
Description (OCR text may contain errors)
United States Patent Ohfuka et a1.
[ Dec. 16, 1975 PERCENT TRANSMITTANCE (70) HYGROSCOPIC ACRYLIC SYNTHETIC FIBERS AND METHOD FOR PREPARING THE SAME Inventors: Toshio Ohfuka; Yoshihisa Schichijo;
Yasushi Ichikawa; Katsuo Yamamoto, all of Fuji, Japan Asahi Kasei Kogyo Kabushika Kaisha, Osaka, Japan Filed: Sept. 6, 1973 Appl. No.: 394,937
Related US. Application Data Continuation-in-part of Ser. No. 138,875, April 30, 1971, abandoned, which is a continuation-in-part of Ser. No. 30,540, April 20, 1970, abandoned.
Foreign Application Priority Data May 8, 1969 Japan 44-34782 U.S. C1.260/85.5 S; 260/855 R; 260/855 AM;
260/855 N; 260/855 B; 260/8072; 260/65; 260/8073; 260/793 M; 260/63 N Int. C1. C08F 220/48; C08F 224/; C08F 226/06 Field of Search. 260/855 R, 85.5 AM, 85.5 N, 260/855 B, 80.72, 80.73, 85.55
 References Cited UNITED STATES PATENTS 2,579,451 12/1951 Polson 264/182 3,073,669 1/1963 Fujisaki et a1. 264/182 3,107,971 10/1963 Yasawa et a1 264/182 3,147,322 9/1964 Fujisaki et a1. 264/182 3,287,304 11/1966 Fujisaki et a1 260/296 AN 3,399,161 8/1968 Ichikawa et a1 264/182 3,410,941 11/1968 Dagon 264/182 Primary Examiner.1oseph L. Schofer Assistant ExaminerMaria S. Tungol Attorney, Agent, or Firm-Fred Philpitt  ABSTRACT Acrylonitrile polymer fibers having an improved bygroscopicity areprepared by hydrolyzing an acrylonitrile copolyrner comprising 0.5 to 10% by weight of N,N-substituted amide, 0 by weight of an ethylenically unsaturated compound copolymerizable with acrylonitrile and at least by weight of acrylonitrile in nitric acid to give a degree of hydrolysis as expressed by ODR of 1680 cmto 1450 cm-' in the range of 1.2-1.8,.f0l1owed by conventional wet spinning by using nitric acid as a solvent.
2 Claims, 3 Drawing Figures INFRARED ABSORPTION SPECTRUM WAVE NUMBERS -U.S. Patent Dec; 16, 1975 Sheet 1 of2 3,926,930
INFRARED ABSORPTION SPECTRUM \|3'0o\||'00 \9'00 \700 \500 I600 I400 I200 I000 800 600 O O O O O O 6 5 4 3 2 I.
WAVE NUMBERS (cm') US. Patent INFRARED ABSORPTION SPECTRUM ABSORBANCE 4000 3500 3000 2500 I I900? I700 I I500 I500 I100 \900 3700 I 500 2000 I800 I600 I400 I200 WAVE NUMBERS TANGENT TANGENT WAVE NUMBERS (Cm' I-IYGROSCOPIC ACRYLIC SYNTHETIC FIBERS :AND METHOD FOR PREPARING THE SAME This application is a continuation-in-part application of Ser. No. 138,875, filed Apr. 30, 1971, which in turn is a continuation-in-part of Ser. No. 30,540,'filed Apr. 20,-1970. Both applications are now abandoned. The benefits of 35 USC 120 are claimed with respect to these prior related applications.
DESCRIPTION OF THE INVENTION fibers, because they are widely applied to such articles as underwear. baby wear, socks, blankets, etc. The acrylonitrile fibers containing acrylonitrile as a main component have excellent physical and chemical properties, but their hygroscopicity is especially small among the various fibers and this is a great practical disadvantage.
Many attempts have been made to improve the hygroscopicity of the acrylonitrile polymer fibers, but acrylonitrile polymer fibers having a hygroscopicity comparable with that of the natural fibers, and at the same time, sufficient practical functions as a fiber, have not been discovered yet.
So far proposed hygroscopic synthetic fibers have been prepared by subjecting fibers or knitted or woven cloth, to resin treatment, chemical treatment or graft polymerization of hydrophilic monomers. However, glutinous cohesion between fibers is liable to take place, and the shape, gloss, whiteness, feeling and touch of the fibers are considerably impaired. Waterabsorbing property may be endowed thereby, but the true hygroscopicity or permanency is impaired.
Further, in a method for mixing polymers or a spinning dope witha hydrophilic substance or hygroscopic substance, there are'only a small number of suitable substances and the permanency has not been satisfied. The spinnability, gloss, feeling and touch have been inevitably lowered.
Furthermore, in the case of fibers composed of a copolymer with a hydrophilic ethylenic unsaturated compound containing a carboxylic-acid, sulfonic acid, amines and their salts hydroxyl group, primary amide, etc'. unless a large amount of hydrophilic compound is used, satisfactory hygroscopicity cannot be obtained 2 ability, etc., and a good fiber form. feeling. touch. physical properties and dyeability.
The acrylonitrile polymer fibers of the present invention comprise acrylonitrile polymer fibers having a moisture regain of 3.0% to 10.0% at a relative humidity of 65% at 20C, and consist of a nitric acid-hydrolyzate of a polymer comprising at least by weight of acrylonitrile, 05-10% by weight of N,N-substituted acrylor methacrylamide having the general formula of (wherein R represents a hydrogen atom or a methyl group; R and R represent alkyl groups having 1 to 3 carbon atoms, the sum total of carbon atoms of R. and R being not more than 4 or R and R being cyclically connected to each other to form a pyrrolidine or morpholine structure) and optionally a balance of an ethylenically unsaturated compound copolymerizable with acrylonitrile, having such a degree of hydrolysis that an amide group of 1680 cm is formed in the infrared absorption spectrum and the ODR of 1680 cm to 1450 cm is in the range of 1.2l.8.
It has been heretofore well known that acrylonitrile type polymers are hydrolyzed by an acid but hydrolysis greatly reduces the heat stability and mechanical properties of the polymers and also reduces spinnability at the time of fiber production. Accordingly, it has been a conventional procedure to suppress the tendency of hydrolysis as much as possible in prior art. We have found thatthe acrylonitrile copolymer with the amides represented by a general formula (Ilcan be hydrolyzed quickly by an acid and its hydrophilic property can be improved thereby, and in spite of such an advantage, the reduction of heat stability and physical properties are very small.
The hydrolysis of the copolymers of acrylonitrile with primary amide or secondary amide such as acrylamide or methacrylamide, N-monosubstituted acrylamide or N-monosubstituted methacrylamide which are considered to be homologs of the amides of the general for.- mula (I), carried out by acid is very slow, improvement of hydrophilic property is small, reduction of heat stability, physical properties and spinnability are large (see Example 2).
When 05-10% by weight of the N,N-substituted acrylamide or methacrylamide as represented by the structural formula (I) is contained in the copolymer, a good effect can beattained according to the present invention. If the copolymer contains less than 0.5% by weight of N,N-substituted acrylamide or methacrylamide, the increase in the hydrophilic property is small. If the copolymer contains more than 10% by weight of N,N-substituted acrylamide or methacrylamide, the reduction of physical properties becomes larger and practical functions as fibers are lowered. Therefore, the use of the copolymer containing less than 0.5% or more than 10% by weight of N,N-substituted acrylamide or methacrylamide is not preferable.
Furthermore, when the copolymer contains less than 85% by weight of acrylonitrile, good physical and chemical properties of acrylonitrile polymer fibers cannot be obtained.
erty of the polymer is lowered. Therefore I to 4 carbon 5 atoms are preferable.
Amides in case where both of R. and R or either R or R of N.N-substituted (meth) acrylamide of the formula I) is hydrogen atom. for example, acrylamide.
methacrylamide, N-methylacrylamide, N-methylmethacrylamide, etc. have only a small hydrolysis rate in an acid, and therefore improvement of hygroscopicity is poor, and furthermore the thus obtained fibers show poor heat stability and undergo considerable discoloration. and impairment of physical properties resulting in notable degradation of practical functions as fibers. The N.N-substituted acrylamides or methacrylamides represented by the structural formula (I) in the present invention include the following compounds:
CH CHCOl\l(CH;,) (N.N-dimethylacrylamideJ CH CCON(CH, (N.N-dimethylmethacrylamideJ CH1! CH CHCON (N-methyLN-ethylacrylamide) C:H CH3 1; CH CCON (N-methyl-N-ethyl- H methacrylamide) CH;- CHCON(C- H.-,): (N.N-diethylacrylamide) Of course, it is possible to copolymerize other kinds of ethylenically unsaturated compounds with acrylonitrile and a compound represented by the general formula (I) in a balanced amount.
Examples of the ethylenic unsaturated compounds copolymerizable with acrylonitrile used in the present invention include alkyl acrylates such as methyl acrylate, ethyl acrylate, etc.; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, etc.; vinyl esters such as vinyl acetate; unsaturated ketones such as methylvinyl ketone, etc.; vinyl ethers; styrene and its alkyl derivatives; vinyl halides such as vinyl chloride,
vinyl fluoride, vinyl bromide, vinylidene chloride, etc.; vinylpyridines such as 2-vinylpyridine, 2-methyl-5- vinylpyridine, etc.; N,N-diethylaminoethyl methacrylates; sulfonic acids such as allylsulfonic acid, styrene sulfonic acid and their salts. I
The copolymers of the present invention canbe prepared according to various well known procedures, and there is no particular limitation thereto.
Even if the copolymers of N,N-substituted acrylamidc or methacrylamide as shown by the structural formula (l) and acrylonitrile of the present invention are spun using the well known solvents for the acrylonitrile polymer other than concentrated acids. for example,
-N.N-dimethylformamide, N.N-dimethylacetamide, di-
methylsulfoxide, a concentrated aqueous solution of zinc chloride, a concentrated aqueous solution of rhodanates, etc., no hydrolysis occurs, and hence improvement in the hygroscopicity of the thus obtained fibers can scarcely be observed (reference is made to Example I).
This fact is due to the notable increase of hydrophilic property by the hydrolysis with acid, of the acrylonitrile polymers of the present invention.
As for acids, those other than nitric acid are also useful, but, from the viewpoint of solubility, spinnability. physical properties, etc., nitric acid is most suitable.
FIG. I shows infrared absorption spectra of the copolymer used in the present invention.
FIG. 2 shows infrared absorption spectra of the fibers obtained by spinning a copolymer by wet process in a nitric acid system.
FIG. 3 is a figure illustrating ODR (optical density ratio) employed in the present invention.
As shown in the infrared absorption spectra in FIGS. 1 and 2, when the copolymers of the present invention are subjected to acid hydrolysis, the absorptions at 2250 cm and 1630 cm which are characteristic absorptions of acrylonitrile and the amides represented by the general formula (I), are reduced, and a new characteristic absorption which has not been observed before hydrolysis appears at I680 cm.
The hydrolysis mechanism and hydrolyzed product have not all been clarified yet. However, it is presumed 5 from the fact that the nitrile groups of the fibers after hydrolysis are less than those of the original polymer, that the hydrolysis product be that formed by the reaction of the nitrile groups adjacent to the amide expressed by the formula (I), with the amide expressed by the formula (I), followed by hydrolysis. Further, in this hydrolysis, it is presumed that the amides expressed by the formula (I) are hydrolyzed easier than primary or secondary amides, due to an autocatalysis in the pres-' ence of acid, since the electronegativity of the nitrogen atom of the N,N-substituted amides expressed by the formula (I) is higher than those of primary or secondary amides due to the electron inductive effect of the alkyl group.
The characteristic absorption. at 1680 cm formed by the hydrolysis is in accordancewith the characteristic absorption of acrylamide, but even when it is assumed that the hydrolysis product be an acrylamide, and a polymer is prepared by copolymerizing acrylonitrile, acrylamide and N,N-dimethylacrylamide so as to give the infrared absorption spectra and absorbance identical with those of the hydrolysisproduct of the present invention and the resulting polymer is spun with N,N-dimethylformamide, the moisture regain of the thus obtained fibers is remarkably smaller than that of the hydrolysis product (see Comparative Example 1). It seems from this fact that the hydrolysis product may be a hydrophilic substance other than the acrylamide, but even if it is acrylamide, the arrangement of the acrylamide formed by the hydrolysis in the polymer chain is different from that obtained by the copolymerization, which results in the difference of hygroscopic property and physical properties. Further, the homopolymer of the amide represented by the general formula (I) hardly undergoes hydrolysis in contrast to its copolymer with acrylonitrile. It is really surprising that the effect of the present invention can be attained only by the acid hydrolysis of the copolymer of acrylonitrile and the amide represented by the general formula (I).
In the hydrolysis of the copolymers of acrylonitrile and the amide represented by the general formula (I), of the present invention, the degree of acid hydrolysis must be limited as hereinafter defined so'as to satisfy the object of the present invention. If the degree of acid hydrolysis is small, the increase of hygroscopicity is insufficient, and a. too large degree of acid hydrolysis is not preferable, becausephysical properties of fibers are reduced.
The degree of acidhydrolysis of Y the present invention can be expressed'by the Optical Density Ratio (hereinafter referred to as ODR)-of the characteristic absorption of the infrared spectrum.
Optical Density Ratio (ODR) is a ratio of optical densities of each characteristicabsorption e.g. a ratio of log (b/a) log (d/c) in FIG. 3. In case of the present invention, the absorption of -CI-I 1450 cm, which does not change before and after the hydrolysis, is selected as a standard value. The infrared absorption spectra herein referred to were measured using Hitachi ,GP-II type spectrograph according to KBr tablet method with the amount of sample of 2 mg/200 mgKBr.
As for the degree of hydrolysis in the present invention, it is preferable that the ODR of absorption at 1680 cm, of amide formed by hydrolysis to absorption of methylene group at 1450 cm be in the range of 1.2 to 1.8. If ODR. is smaller than 1.2, the degree of hydrolysis is not sufficient, hygroscopicity is low and not satisfactory for the object of the present invention. If ODR is greater than 1.8, the amount of amide is larger, which results in the reduction of physical properties of fibers and degradation of heat stability. The degree of hydro- 6. lysis in this range gives a moisture regain in the range of 3.0-l0.0% at 20C and 65% RH.
Even in case of polymers other than the copolymers of acrylonitrile with amides expressed by the general formula (I), of the present invention, such as copolymer of acrylonitrile with acrylamide or acrylonitrile homopolymer, it is possible to bring the ODR to a value in the range of the present invention by acid hydrolysis, but the resultant moisture regain is always low and does not reach the expected value of the present invention.
When the degree of hydrolysis is larger over the ODR value of the present invention. moisture regain greater than 3% can be attained but the reduction of fiber properties is remarkable and degradation is so great that their commercial value is lost.
The hydrolysis conditions are selected depending upon the copolymerized amount of the amide represented by the general formula (I) in the copolymers of acrylonitrile with the amide represented by the general formula (I).
As for the concentration of nitric acid, 55 is preferable. If it is lower than 55%, the solubility of the copolymer is bad, and if it is higher than 85%, whiteness of hydrolysis product becomes worse due to evolution of nitrous acid. This is not preferable.
As for the temperature of hydrolysis, when a temperature of 10C or higher is selected. hydrolysis can be carried out using only a small copolymerized amount of the amide represented by the general formula of (I) and within a short period of time.
For the production of fibers, the nitric acid solution of hydrolysis product after the acid hydrolysis, as it is, can be used as a spinning solution and a conventional nitric acid spinning process can be employed.
Now, the present invention will be explained, referring to non-limitative Examples.
Example I A. 3750 g. of acrylonitrile, 250 g. of N,N-dimethylacrylamide and 50 l of water were added to a 1 capacity polymerization reactor with a stirrer and mixed together. Then, 40 g. of ammonium persulfate and 200 g. of sodium hydrogen sulfite were added thereto and the resulting mixture was adjusted to pH 2.8 with sulfuric acid. Then, the polymerization reaction was carried out at 60C for 5 hours. The resulting copolymer was thoroughly washed with water, dehydrated and dried at 70C for 10 hours.
The resulting polymer contained 94.3% by weight of acrylonitrile and 5.7% by weight of N,N-dimethylacrylamide (polymer a The polymer (1 was dissolved in 65% nitric acid at 0C to make its concentration 16% by weight. After the resulting solution was kept at 0C for 3 hours, the temperature of the solution was elevated to 20C at which temperature hydrolysis was carried out for 12 hours. Thereafter the solution was cooled to 5C, and then extruded from spinning nozzles 100 holes X 0.08 mm) into a 30% aqueous nitric acid solution at 0C to coagulate the resulting extrudate. After water washing, the extruded fibers were stretched to 8 times the original length in boiling water and dried. Then, the fibers were subjected to wet heat treatment at C thereby to form fibers of 3 deniers.
Infrared absorption spectra of the polymer a and the fibers obtained by the nitric acid hydrolysis and the wet spinning in the nitric acid system are given in FIGS. 1 and 2.
Separately, the polymer a was dissolved in dimethyl- -continued forrnamide at 40C to give a concentration of 17% by (Acrykmimlc 943,7! weight. The resultmg solution was'extruded mm a 50% 9 aqueous dimethylformamide solution at 30C. washed d w1th water. stretched to 8 times the original length in 5 Polymer e *AcrZvlnnitrile 100.11% boiling water. dried and then subjected to wet heattreatment at 120C thereby to form fibers of 3 deniers. Each of these polymers was dissolved in 70% nitric a O y; z ggl i lzfi i i i g ggg fibers acid at 15C to glve a concentration of 15% by weight. e I y O c are glven e 0 at which temperature hydrolysis was carried out for 18 hours. Thereafter the resulting solution was cooled to 0C and then extruded from spinning nozzles 100 Add Mfisture ODR holes X 0 08 mmda) into a 35% aqueous nitric acid at treatstrength strength regain (l680cm V Remarks q mm M M 1 -1, 0 C to coagulate the extrudate. After water washmg,
the extruded fibers were stretched to 7 times the ori i- Example g 3m 3,45 637 141 nal length 1n botlmg water, and dried. Then the fibers present were subjected to wet heat treatment at l 10C to form fibers of 5 deniers. None 3.36 2.71 L88 0 tive The physical properties of the resulting fibers at C Example and 65% relative humidity were as follows:
Mois- ODR Dry Wet ture (l680cm"/ Hunter Polystrength strength regain l450cm) white- Remarks mer g/d g/d 71 ness Example of b 2.97 2.50 4.75 [.44 63.5 the present invention c 2 83 2.26 3.99 1.02 56.7 Comparative Example d 2.54 L89 2.78 1.60 49.2 Comparative Example e 2.02 1.43 .0l 0.53 47.8 Comparative Example Hunters whiteness referred to in the present inven- 40 tion is given as follows: The fibers obtained by the hydrolysis were rich in Hunters whiteness 00 "(]0() L)2 gloss and flexibility and had a cool feeling when touched with hands wherein L means brightness and a a is expressed by The moisture regain referred to in the present inveng fi tone of red'green and b by that of yellow' tion is iven accordin to the followin measurin method? g g g The fibers obtained from the polymer b of the present Fibers' of sample are scoured and then dried at invention were good in both moisture regain and whiteand under a reduced pressure of 700 mm Hg till the ness whereas the fibers obtamfad from the C weight reaches a constant value. The resulting dry and Polymer were. both. low m ODR and molsyure weight is weighed. After drying, the fibers are allowed regam and also bad m whltenes' fibers obiamed to stand for one week in a desiccator containing a satug g. p d L x. g regam and ratedaqueous solution of sodium nitrite (RH. 65%). a m w 1 eness m Splte 0 lg Thereafter the weight is again weighed (wet weight). Example 3 Moisture regam is given according to the following 5 Pol mers havm the followin com ositrons were equation. y g p prepared in the same manner as in Example 1:
(Wet weight (Dry weight f fibers offihgrs) r7 Polymer NN-dlmethylacrylamlde Acrylonltnle regam (Dry weight of fibers) g h 9.5% 90.5% 1 11.9% 83.1%
Example 2 Polymers having the following compositions were Each Q thesfi P ym w j q 'f nitric acid prepared in the Same polymerization method as i E hydrolysis under the condltions described In the following Table, and then spun in the same manner as in ample 1:
N.N-dimeth vlmethacrylamide Example 1 to give fibers of 3 deniers. The physical properties of the resulting fibers at 20C and 65% relative humidity are shown in the next Table.
Table Conditions Dry Wet ODR Moisture Hunters No. Polymer of strength strength l680cm"/ regain whiteness Remarks hydrolysis g/d g/d l450cm 1 f 70% HNQ, 2.56 2.07 0.78 2.27 52.4 Comparative C 20hrs. Example 2 ditto 70% HNO 2.11 1.53 1.11 2.62, 47.5 ditto C 20hrs. 3 ditto 70% HNQ, 1.62 1.02 1.45 2.93 42.1 ditto CX20hrs. 4 g HNO, 2.88 2.36 1.04 2.95 55.2 ditto 20C 20hrs. 5 ditto 70% HNO 2.53 .27 1.29 3.51 52.3 Example of 30CX20hrs. the present invention 6 h 65% HNQ 2.76 2.63 1.45 4.85 61.9 ditto 10C Z0hrs. 7 ditto 65% HNO 2.59 2.32 1.59 8.05 60.1 ditto 20C 20hrs. 8 r 65% HNQ, 2.48 1.97 1.73 6.25 60.7 Comparative 10C 20hrs. Example 9 ditto 65% HNO 2.11 1.69 1.82 7.98 58.3 ditto 15CX20hrs According to Experiments Nos. 1 and 2, the resulting fibers were low in both ODR and moisture regain and also bad in whiteness due to the small copolymerized amount of the comonomer expressed by the general formula (I), in spite of the fact that they were hydrolysis products. As for No. 3, the ODR was increased up to a given value of the present invention by employing severe conditions of hydrolysis, but the moisture regain was still low due to the small copolymerized amount of the comonomer expressed by the general formula (I), and a hydrolysis other than that caused by the structure of the formula (I) occurred due to the severe conditions of hydrolysis, which results in a higher ODR, but degradations in the physical properties and whiteness were remarkable. As for No. 4, although the copolymerized amount of the comonomer expressed by the general formula (I) fell within the range of the present invention, the ODR and moisture regain were both low due to the still small copolymerized amount. Thus, the hydrolysis conditions must be made severer up to those of No. 5. However, when the copolymerized amount of the comonomer expressed by the formula (I) is small, the whiteness is reduced by the conditions of hydrolysis made severe due to the small amount, and hence it is preferable that the copolymerized amount is 3% or more. Nos. 6 and 7 are Examples of the present invention. As for No. 8, the ODR and moisture regain reached a given value of the present invention due to the large copolymerized amount, but reduction in strength was great due to the large copolymerized amount, and also the balance of performances of fibers was broken. As for No. 9, reduction in strength was similarly remarkable.
Example 4 A copolymer consisting of 93.7% by weight of acrylonitrile and 6.3% by weight of acryloyl morpholine prepared in the same manner as in Example 1, was subjected to hydrolysis for 12 hours in a nitric acid at 20C. After cooling, the resulting solution was extruded from spinning nozzles (100 holes X 0.06 mmtb) into a 35% nitric acid aqueous solution to coagulate the extrudate. After water washing, the resulting fibers were stretched to 7 times the original length by heating with steam. After drying, they were heat-treated at l 10C to obtain fibers of 2 deniers. The physical properties of the resulting fibers at 20C and 65% relative humidity were as follows:
ODR 1.48 Moisture regain 7.15% Dr strength 3.03 Wet strength 2.76 Hunter's 61.7
whiteness What is claimed is:
l. A polymer hydrolyzate produced by hydrolyzing with nitric acid a polymer comprising at least by weight of acrylonitrile, 0.5 10% by weight of N,N- substituted acrylor methacryl-amide having the general formula of (wherein R represents a hydrogen atom or a methyl group; R and R represent alkyl groups having 1 to 3 carbon atoms, the sum total of carbon atoms of R and R being not more than 4, or R and R being cyclically connected to each other to form a pyrrolidine or morpholine structure) and 0 15% by weight of a compound selected from the group consisting of methyl acrylate. ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, methyl vinyl ketone, styrene, vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, 2-vinylpyridine, 2-methyl-5-vinylpyridine, N,N-diethylaminoethyl methacrylates, allysulfonic acid and styrene sulfonic acid, the hydrolysis being carried out to such a degree that an amide group of 1680 cm is formed in the infrared absorption spectrum and the ODR of 1680 cm to 1450 cm is in the range of 1.2 1.8, said polymer hydrolyzate having a moisture regain of 3.0 to 10% at a relative humidity of 65% at 20C.
2. Fibers of acrylonitrile polymers according to claim 1 wherein said N,N-substituted acrylor methacrylamide is N,N-dimethylacrylamide or N,N-dimethylmethacrylam ide.